Thermodynamic Modelling of Superfluid Stirling Cryocoolers

2019 ◽  
Author(s):  
G.-R. Domenikos ◽  
P. Bitsikas ◽  
E. Rogdakis
Keyword(s):  
Superfluid Helium ◽  
Temperature Limit ◽  
Cryogenic Temperatures ◽  
Normal Fluid ◽  
Atomic Spin ◽  
Working Medium ◽  
Working Media ◽  
Lambda Line ◽  
Stirling Refrigerator ◽  
Cooling Procedure

Abstract The aim of this paper is to describe and thermodynamically model cryogenic Stirling refrigerators, using Helium in its different forms as the working medium. Helium has unique properties at cryogenic temperatures forming a superfluid. The cryogenic Stirling refrigerators with Helium at such low temperatures make use of the properties of this superfluid nature of Helium, thus they are referred to as Superfluid Stirling Refrigerators (SSR). To make use of these remarkable properties of superfluid helium a different version of Stirling refrigerator is used where superleaks are introduced in the pistons in order to let the superfluid part flow freely but constrain the normal fluid. This cooling procedure has an upper temperature limit as it is based on the superfluidity of helium, hence all the workings of this cycle must be well below the Lambda line. In addition, different models are needed and are used for the different isotopes of helium as their atomic spin nature is different and therefore their behavior at temperatures near absolute zero. In this study of SSR cryocoolers great care is being given towards the thermodynamic behavior of the entire system and working media, as well as different designs of the apparatus.

Improving the efficiency and reliability of electric power generation at incineration plants

2020 ◽  
Vol 12 (4) ◽  
pp. 281-285
Author(s):  
A. V. Martynov ◽  
N. E. Kutko
Keyword(s):  
Low Temperature ◽  
Power Plants ◽  
Thermal Power ◽  
Moscow Region ◽  
Capital Costs ◽  
Working Medium ◽  
The Creation ◽  
Working Media ◽  
Near Future ◽  
Efficiency And Reliability

The article deals with the problem of waste disposal and, accordingly, landfills in the Moscow Region, which have now become the number 1 problem for the environment in Moscow and the Moscow Region. To solve this problem, incineration plants (IP) will be established in the near future. 4 plants will be located in the Moscow Region that will be able to eliminate 2800 thousand tons of waste per year. Burning of waste results in formation of slag making 25% of its volume, which has a very high temperature (1300.1500°C). An arrangement is considered, in which slag is sent to a water bath and heats the water to 50.90°C. This temperature is sufficient to evaporate any low-temperature substance (freons, limiting hydrocarbons, etc.), whereupon the steam of the low-temperature working medium is sent to a turbine, which produces additional electricity. The creation of a low-temperature thermal power plant (TPP) increases the reliability of electricity generation at the IP. The operation of low-temperature TPPs due to the heat of slag is very efficient, their efficiency factor being as high as 40.60%. In addition to the efficiency of TPPs, capital costs for the creation of additional devices at the IP are of great importance. Thermal power plants operating on slag are just such additional devices, so it is necessary to minimize the capital costs of their creation. In addition to equipment for the operation of TPPs, it is necessary to have a working medium in an amount determined by calculations. From the wide variety of working media, which are considered in the article, it is necessary to choose the substance with the lowest cost.

Influence of Imperfections in the Working Media on Diesel Engine Indicator Process: Part 2 — Results

1998 ◽  
Author(s):  
Stanislav N. Danov ◽  
Ashwani K. Gupta
Keyword(s):  
Mathematical Model ◽  
Diesel Engine ◽  
High Pressures ◽  
Combustion Process ◽  
Ideal Gas ◽  
Working Medium ◽  
High Pressures And Temperatures ◽  
Specific Heat Capacities ◽  
Working Media ◽  
The Mathematical Model

Abstract In the companion Part 1 of this two-part series paper several improvements to the mathematical model of the energy conversion processes, taking place in a diesel engine cylinder, have been proposed. Analytical mathematical dependencies between thermal parameters (pressure, temperature, volume) and caloric parameters (internal energy, enthalpy, specific heat capacities) have been obtained. These equations have been used to provide an improved mathematical model of diesel engine indicator process. The model is based on the first law of thermodynamics, by taking into account imperfections in the working media which appear when working under high pressures and temperatures. The numerical solution of the simultaneous differential equations is obtained by Runge-Kutta type method. The results show that there are significant differences between the values calculated by equations for ideal gas and real gas under conditions of high pressures and temperatures. These equations are then used to solve the desired practical problem in two different two-stroke turbo-charged engines (8DKRN 74/160 and Sulzer-RLB66). The numerical experiments show that if the pressure is above 8 to 9 MPa, the working medium imperfections must be taken into consideration. The mathematical model presented here can also be used to model combustion process of other thermal engines, such as advanced gas turbine engines and rockets.

scholarly journals THE METHOD OF PROCESSING EXPERIMENTAL DATA AND THE ALGORITHM FOR ITS IMPLEMENTATION TO DETERMINE THE PARAMETERS OF THE RHEOLOGICAL MODEL OF A DILATANT LIQUID WITH THE EFFECT OF «SOLIDIFICATION»

2021 ◽  
pp. 101-106
Author(s):  
В.Н. Колодежнов ◽  
А.В. Колтаков ◽  
С.С. Капранчиков ◽  
А.С. Веретенников
Keyword(s):  
Experimental Data ◽  
Shear Rate ◽  
Rheological Model ◽  
Sharp Increase ◽  
Solid Phase ◽  
Threshold Value ◽  
Viscoplastic Fluid ◽  
High Concentration ◽  
Working Medium ◽  
Working Media

В различных технических приложениях применяются рабочие среды типа суспензий, которые при достаточно высокой концентрации частиц твердой фазы демонстрируют аномалии вязкости. Существо этих аномалий заключается в том, что при приближении скорости сдвига к некоторому пороговому значению наблюдается явление резкого возрастания вязкости жидкости. При этом в соответствующих зонах течения рабочая среда начинает вести себя подобно твердому телу. Механическое поведение такой рабочей среды может быть описано в рамках реологической модели вязкопластической жидкости, которая позволяет учитывать проявление эффекта“упрочнения” или “отвердевания”. Рассмотрена методика определения параметров такой реологической модели на основе обработки экспериментальных данных зависимости касательного напряжения от скорости сдвига. Предложен алгоритм для реализации этой методики. In various technical applications, working media such as suspensions are used, which, at a sufficiently high concentration of solid phase particles, demonstrate viscosity anomalies. The essence of these anomalies lies in the fact that when the shear rate approaches a certain threshold value, the phenomenon of a sharp increase in the viscosity of the liquid is observed. At the same time, in the corresponding flow zones, the working medium begins to behave like a solid. The mechanical behavior of such a working medium can be described within the framework of a rheological model of a viscoplastic fluid, which allows for the manifestation of the effect of “hardening” or “solidification”. The method of determining the parameters of such a rheological model based on the processing of experimental data on the dependence of the shear stress on the shear rate is considered. An algorithm for the implementation of this technique is proposed

scholarly journals Thermodynamic Analysis of Ozone-Safe Low Boiling Working Media for Turbo-Expander Plants

2020 ◽  
Vol 63 (6) ◽  
pp. 554-562
Author(s):  
A. V. Ovsyannik ◽  
V. P. Kliuchinski
Keyword(s):  
Global Warming ◽  
Heat Exchanger ◽  
Thermodynamic Analysis ◽  
Single Component ◽  
Efficiency Coefficient ◽  
Exergetic Efficiency ◽  
Working Medium ◽  
Turbo Expander ◽  
Zero Potential ◽  
Working Media

The article considers 46 low-boiling working media (LBWM) with zero potential for ozone layer destruction. Out of them, 14 ones are single-component hydrofluorocarbon refrigerants, 28 ones are multi-component mixtures of hydrofluorocarbon refrigerants, and the four ones are native refrigerants. Thermodynamic analysis of working media based on the classical turbo-expander scheme with a heat exchanger designed to cool the superheated LBWM that has left the turbo-expander has been performed. For this scheme, a cycle is constructed in T–s-coordinates. The LBWM was compared using the exergetic coefficient of efficiency (KE). In the course of the study, it was found that for some LBWM, the sequence of location of the exergetic efficiencydependences on temperature at thermodynamically optimal working medium pressures is preserved over the entire temperature range under study (from 100 to 300 оC). In other words,if the working medium has the highest exergetic efficiency coefficient, then this property is inherent in it at any temperature in a given interval. It is proposed to perform the analysis of the LBWM for exergetic efficiency at an arbitrarily selected temperature (250 оC). The study demonstrated that the highest exergetic efficiency of natural refrigerants is R600A (50.25 %), among single component hydrofluorocarbon refrigerants – R245FA (50.00 %), R1233ZD(E) (49.91 %), R236EA (49.59 %), among multi-component mixtures of hydrofluorocarbon refrigerants – R429A (47.92 %), R430A (47.49 %) and R423A (47.47 %). Out of the all examined refrigerants, the following ones have the highest exergetic efficiency of all the considered LBWM: R600A, R245FA, R1233ZD(E), R236EA, R1234ZE(Z), R236FA. They belong to both natural refrigerants (hydrocarbons) and single-component hydrofluorocarbons. It should be noted that each of these working media has its drawbacks: some have a high potential for global warming, others are explosive, and others have a high cost.

scholarly journals Combined process of vibratory processing and oxidation with the use of polymeric environments

2020 ◽  
Vol 210 ◽  
pp. 01006
Author(s):  
Vladimir Ivanov ◽  
Sergey Popov ◽  
Nikolai Dontsov ◽  
Nikolai Ryzhkin ◽  
Julia Oleynikova ◽  
...  
Keyword(s):  
Oxide Film ◽  
Oxide Coating ◽  
Oblique Impact ◽  
Combined Process ◽  
Working Medium ◽  
Working Media

Studies were carried out to combine vibration processing and oxidation in polymer working media, which allowed to combine three technological stages. Characteristic traces of direct and oblique impact of the polymer working medium, along the surface of the metal with oxide film, are determined. Studies of the structure of the nanorelief of the vibrational chemical-mechanical oxide coating and the main parameters of the process are.

scholarly journals Quantum Heat Engines with Complex Working Media, Complete Otto Cycles and Heuristics

Entropy ◽  
2021 ◽  
Vol 23 (9) ◽  
pp. 1149
Author(s):  
Ramandeep S. Johal ◽  
Venu Mehta
Keyword(s):  
Upper Bound ◽  
Necessary Conditions ◽  
Engine Performance ◽  
Extreme Case ◽  
Arbitrary Spin ◽  
Spin Model ◽  
Heat Engines ◽  
Working Medium ◽  
Working Media ◽  
Quantum Heat Engines

Quantum thermal machines make use of non-classical thermodynamic resources, one of which include interactions between elements of the quantum working medium. In this paper, we examine the performance of a quasi-static quantum Otto engine based on two spins of arbitrary magnitudes subject to an external magnetic field and coupled via an isotropic Heisenberg exchange interaction. It has been shown earlier that the said interaction provides an enhancement of cycle efficiency, with an upper bound that is tighter than the Carnot efficiency. However, the necessary conditions governing engine performance and the relevant upper bound for efficiency are unknown for the general case of arbitrary spin magnitudes. By analyzing extreme case scenarios, we formulate heuristics to infer the necessary conditions for an engine with uncoupled as well as coupled spin model. These conditions lead us to a connection between performance of quantum heat engines and the notion of majorization. Furthermore, the study of complete Otto cycles inherent in the average cycle also yields interesting insights into the average performance.

scholarly journals The concept of a passive heat transport system from solar collectors

2020 ◽  
Vol 154 ◽  
pp. 05005
Author(s):  
Daniel Chludziński ◽  
Michał Duda ◽  
Piotr Sołowiej ◽  
Joann Hałacz ◽  
Andrzej Lnage
Keyword(s):  
Heat Transport ◽  
Transport System ◽  
Operating Conditions ◽  
Working Medium ◽  
Low Energy Consumption ◽  
External Sources ◽  
Working Media ◽  
The One ◽  
The Right ◽  
Heating Medium

The paper presents a concept of building a passive heat transport system based on the use of an antigravity thermosyphon with a bubble pump. Such solutions are suggested when the heat source is located above the place of its reception, e.g. in the case of solar collector installations. One of the components of the system is the device forcing the circulation of the heating medium. In the presented system, this process is carried out without the use of additional external sources of energy, such as electricity, to supply the circulating pumps. Such an installation is autonomous, so the risk of failure is diminished. It is also possible to automatically adjust the system to changing operating conditions without the need for additional automation. Other known solutions of this type are not used due to their imperfection. The challenge is to select the right working medium, whose physical properties should on the one hand transmit as much heat as possible, and on the other hand enable the pumping of the heating medium to be performed with low energy consumption. In the opinion of the authors of the paper, it is possible to achieve with the use of two working media in one system: water and a substance with a low boiling point.

Visualization Technique for Determining the Structure Functions of Normal-Fluid Turbulence in Superfluid Helium-4

2012 ◽  
Vol 171 (5-6) ◽  
pp. 497-503 ◽  
Author(s):  
W. Guo ◽  
D. N. McKinsey ◽  
A. Marakov ◽  
K. J. Thompson ◽  
G. G. Ihas ◽  
...  
Keyword(s):  
Superfluid Helium ◽  
Structure Functions ◽  
Visualization Technique ◽  
Normal Fluid ◽  
Fluid Turbulence ◽  
Helium 4
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